1. Field of the Invention
This invention relates to ultrasonic surgical instruments useful in removing tissue from within a biological structure, and more particularly to an improved ultrasonic surgical handpiece employing a transducer and an angled connecting body, and to an improved method of producing such an instrument.
2. Description of the Prior Art
Ultrasonic surgical instruments, generally referred to as handpieces, first met acceptance for use in eye surgery, particularly in the removal of cataracts, and presently are widely used for various surgical procedures. The known ultrasonic handpieces generally employ piezoelectric or magnetostrictive transducers capable of transforming high frequency electrical energy into mechanical impulses or vibrations and essentially consist of an elongated transducer having one end rigidly joined, as by brazing or welding, to an elongated connecting member which, in turn, supports an elongated operative probe or tip on its other end. The vibrating electromechanical assembly, including the transducer, connecting member and probe, are supported by a housing through connecting means which isolates the housing from the mechanical vibrations and provides connections for cooling fluid for the assembly and electrical energy to drive the transducer. Known ultrasonic handpieces of this general type are disclosed, for example, in U.S. Pat. Nos. 3,693,613 and 3,805,787.
The known ultrasonic handpieces in which the operative probe extends coaxially with the housing generally are constructed as 3/4.lambda. transducers, i.e., the length of the transducer and connecting member constitute 3/4 of a wavelength, and a matched 1/4.lambda. tip operative probe mounted on the connecting member completes the full wavelength, with the tip connecting plane being at or closely adjacent to the nodal plane. While these ultrasonic handpieces are widely used in the surgical theatre, their straightline design limits their utility for certain procedures. For example, when the operative site is deep within a biological body, good visibility is not always possible since the housing and the surgeon's hand supporting the housing may interfere with the line of sight to the operative tip. Also, such prior art straight ultrasonic handpieces are of particularly limited utility in microsurgery because the handpiece and the surgeon's hand interfere with the operating microscope.
One attempt to provide an ultrasonic surgical handpiece to overcome the difficulties of the straight handpieces described above is disclosed in U.S. Pat. No. 4,526,571. In this prior art device, a conventional straight transducer assembly is employed to the conventional nodal point mounting for the operative tip, but a 1/2.lambda. curved extension is inserted between the operative probe and its conventional mounting point to provide in effect, a 3/4.lambda. extension in which the longitudinal axis of the operative tip is displaced at an angle, for example, 15.degree., from the longitudinal axis of the transducer assembly. This assembly has successfully solved the problem of visibility at the operative site when working in a deep, restrictive access body opening, but the added length of the overall assembly may reduce the ability of the device to be used in conjunction with an operating microscope in certain conditions. Further, some surgeons accustomed to handling the shorter straight handpieces find it difficult to interchange the longer handpiece because of the difference in maneuverability and balance. Thus, there remains a need for an improved surgical handpiece designed to provide improved visibility at the operative tip and to provide minimal interference with an operating microscope.
It is also known that longitudinal ultrasonic vibrations may be transmitted through an elongated member made up of alternate straight and curved or bent sections. For example, U.S. Pat. No. 3,546,498 discloses a transmission line made up of a series of straight segments joined by short radius bends located at critical locations, i.e., the nodes or antinodes in the transmission element.
A primary object of the present invention is to provide an improved ultrasonic surgical handpiece which overcomes the shortcomings of the prior art handpieces discussed above.
Another object is to provide an improved angled ultrasonic surgical handpiece which is shorter and more maneuverable than the known curved handpieces.
Another object is to provide such an ultrasonic surgical handpiece employing a connecting body which is bent at a location between the nodal and anti-nodal planes adjacent to its ends whereby the axis of the operative tip is disposed at an angle with respect to the axis of the transducer.
Another object is to provide such an ultrasonic surgical handpiece having an improved balance in the surgeon's hand and which is therefore more maneuverable and less fatiguing in use.
Another object is to provide such an improved ultrasonic surgical handpiece for use in connection with operating microscopes and which will not substantially interfere with the use of such microscopes when using at least a 300 millimeter objective lens.
Another object is to provide such an ultrasonic handpiece in which the operative tip and drive components of compatible straight and angled handpieces may be interchanged.
Another object of the invention is to provide a means for producing an angled ultrasonic surgical handpiece which is sufficiently short to be both maneuverable and less fatiguing in the surgeon's hand while not substantially interfering with the use of an operating microscope, and in which a 1/4.lambda. operative tip of a compatible straight handpiece may be employed.